Why does hail appear in the warm season?

In late spring and early summer, sometimes the weather is fine in the morning, and it begins to hail around noon. At this time, although the air temperature is very high, it is spherical, conical or irregular ice that falls; The temperature is very low in winter, but there is no hail. What is the reason?

To understand this truth, we must first know how hail is formed. It turns out that hail and thunderstorm belong to the same family and both come from cumulonimbus clouds, but the cumulonimbus clouds that produce hail have a particularly strong ascending and descending airflow, also called hail clouds. However, this kind of hail cloud that produces hail mostly appears in warm season and rarely appears in cold season. Cumulonimbus clouds are caused by strong air convection and are the product of unstable air.

Secondly, the updraft in this cloud is strong enough to support the increasing hail blocks in the cloud, so the hail in the cloud can merge with snowflakes and water droplets along the way with the rise and fall of the airflow, forming ice cubes with alternating layers of transparency and opacity. When it increases to a certain extent, the updraft can't support it, and it will land on the ground. This is why hail occurs in warm seasons.

In winter, the sun shines obliquely on the ground, and the ground receives weak solar heat, which can not induce strong convection and the air is dry. Even if convection occurs, it is not easy to form tall and bloated cumulonimbus clouds. Even if there is, there will be no heavy hail in the cold season, because the updraft in it cannot be strong enough to support the process of hail formation in the clouds.

Some people may ask: the environmental temperature that forms hail must be very low, but it is very hot in warm seasons. How is the hail formed?

This is because in midsummer, even if the ground temperature is above 30℃, the temperature of the rising air decreases with the height, and the temperature at the cloud bottom is only 20℃; The temperature is below 0℃ about 4 kilometers from the ground in the cloud, and a hail cloud top can extend to more than 10 kilometers from the ground, so there is a low temperature zone below freezing point thick enough in the air to breed hail blocks.